Using Cut Film Daylight Developing Tanks
There seems to be a lot of information about these tanks out here on the web, much of it erroneous. Of the many types that have been made over the years, I have personally used the Combi-Plan, and the Yankee Agitank. In fact, I have both right now. I would like to give a few pointers about using those tanks based upon my own direct experience.
Cut film tanks do not seem to work well with vigorous agitation. Slow and smooth seems to work best. Actually that may be true of all types of tanks. Basically all that is needed is for the old developer near the surface of the film to be replaced by fresh developer periodically. It is not like you are trying to dissolve the emulsion, or something.
Also using dilute developers seem to work best with cut film daylight tanks, my base development for Plus-X/FP4+ 1:1 is 10-11 minutes at 68 degrees. That gives a nice print on grade 3 paper. For printing on grade 2 paper I find 14-15 minutes works better.
The HP COMBI-PLAN Instuction Leaflet
The Combi is a fully invertable tank. It holds 6 sheets of film in a vertical carrier. There are really only two points that I have found to differ with from the instructions.
1. They say to open the cap 1/2 turn. My experience is that if you do not open it a full turn you will get incredibly slow filling and emptying of the chemicals. To make it fill even faster you can curl your fingers under one long edge of the rubber top, and lift it just enough to break the air seal, without letting in light. If you do that it will fill almost as fast as you can pour the chemicals.
2. The instructions say you have to use 35 ounces of chemical for 4x5, I have always used only 1 liter with no problem. (Er..? Upon rereading I notice the instructions equate 35 ounces with 1 liter, so that is not a inconsistancy. Although a liter is usually thought to be 33.8 onces.)
When agitating don't shake the tank. Just turn it upside down around an axis through the wide sides, so the chemicals can flow between the sheets of film, then turn it back the other way to upside down, and then back again to right side up. Do that slowly and smoothly, it ought to take just about 15 seconds to do that twice. I do that (4 inversions) at the top of every minute, and have never had noticably uneven development.
The YANKEE AGITANK Instuction Leaflet
The Agitank is not invertable, this seems to give 35mm photographers fits for some reason. The film carrier holds the film (up to 12 sheets) vertically with the long sides parallel to the top and bottom of the tank. Most of the problems folks have claimed for this tank have to do with uneven development. That in my experience is caused by short developing times, and incorrect agitation.
I have found the proper agitation with the Agitank (which differs from the instuctions) is to simply lift one end from the sink about an inch and set it down gently, then do the same with the other end. If you try this with the tank filled with water and the top off so you can see what is happening, you will see the water slosh back and forth for several seconds afterwards. That is all the agitation these tanks need. I have always done that every 30 seconds, but every minute may work just as well.
Like most cut film daylight tanks these do seem to work better with dilute developers, which give plenty of time to fill, agitate, and drain.